The present invention relates to document image processing and more particularly to duplex document handling.
Duplex copying is an important feature of copier systems operating in businesses. Although, computer storage of document images holds great promise for the future, paper is still the predominant mode of document storage as evidence by rising consumption of paper. A 50% reduction in paper usage is achieved by the use of two-sided documents.
Problems exist however in the handling of two-sided documents in copying and in other office operations such as scanning and faxing. Each page must pass by the scanning system twice, greatly increasing the complexity of the feeder mechanism. Difficulties arise in synchronizing the front page and back page order. When a document containing an odd number of pages are copied onto both front and back sides, often the front page of the document is left as a single sided copy rather than the last page. The same problems may potentially arise in faxing and scanning.
One known solution is described in Japanese Patent No. 7283906 which teaches the use of twin scanner systems including separate CCD sensors so that both the front and the back of a page are scanned in the same pass. This approach requires duplication of not only the CCD sensors but also other scanning hardware and is thus very expensive to implement.
What is needed is an improved economical system and method for handling two-sided documents when copying, scanning, or faxing.
The present invention provides a system and method for handling duplex documents by exploiting bleed-through of the image on the back side of a document. The images of the back sides and front sides of documents are associated with one another to assure correct output in copying, faxing, scanning, etc. This increases reliability and eases recovery from errors including paper jams. The present invention also provides capabilities of avoiding twice duplicated and skipped pages.
A document handling system according to one embodiment of the present invention initially scans in the front side of a page of a multipage document. To select out the bleed-through portions of the scanned in image corresponding to the back side, the system first identifies the connected components in the scanned-in image as corresponding to the front side content. Removing these connected components obtains an image of the back side, from which the system extracts features. Later when the back side of the image is scanned in directly, the same features are extracted so that the back side may be matched to the front. Document inversion detection may also be applied to detect and correct flipped pages.
In accordance with a first aspect of the present invention, a method for handling a document page includes steps of obtaining first side image data, extracting a set of connected components from the first side image data, erasing pixels representing the set of connected components from the first side image data, and extracting a first set of features from the first side image data as processed by the erasing step, whereby the first set of features represents a bleed-through image of a second side of the document page. This bleed-through image may then be matched with the reverse side to detect possible skipped scans.
Other aspects of the present invention take advantage of modern image processing techniques to increase the quality of either simplex or duplex copying. In accordance with a second aspect of the present invention, a method for copying a multipage document includes the steps of scanning in a plurality of document pages to capture image data for each of the plurality of pages, storing the image data for each of the plurality of pages, and comparing the image data for each of the plurality of pages to identify twice scanned pages. This method may be used to prevent the double copying of pages.
A further understanding of the nature and advantages of the inventions herein may be realized by reference to the remaining portions of the specification and the attached drawings.